1. Field of the Invention
The present invention relates to a reaction force apparatus for controlling a reaction force that is applied to the accelerator pedal of a vehicle.
2. Description of the Related Art
Technology has been available in the art for applying an additional reaction force from a motor, in addition to the reaction force from a return spring, to the accelerator pedal of a vehicle (see Japanese Laid-Open Patent Publication No. 2003-260951). According to Japanese Laid-Open Patent Publication No. 2003-260951, a relationship between vehicle speed and a drive signal for a rotational motor (2) is prescribed for each threshold speed, and a reaction force generated by the motor (2) is controlled (see FIG. 2, for example). When the threshold speed changes, the relationship between the vehicle speed and the drive signal for the rotational motor (2) also is changed. For example, when the threshold speed increases, the relationship between the vehicle speed and the drive signal for the rotational motor (2) changes in order to generate a reaction force at a higher vehicle speed (see FIG. 2).
According to Japanese Laid-Open Patent Publication No. 2003-260951, as described above, when the threshold speed increases, the relationship between the vehicle speed and the drive signal for the rotational motor (2) changes in order to generate a reaction force at a higher vehicle speed. If the threshold speed increases while the rotational motor (2) is currently generating a reaction force, then the reaction force, which has been generated so far, changes rapidly. Therefore, the driver of the vehicle may possibly feel discomfort when operating an accelerator pedal (1). In addition, if the accelerator pedal (1) is depressed to different depths, then the amount of reaction force, which is reduced when the threshold speed increases, undergoes irregular differences. As a consequence, individual drivers experience different feelings concerning operation of the accelerator pedal (1), and cannot be guided appropriately to depress the accelerator pedal (1). Moreover, if the reaction force is rapidly reduced when the threshold speed increases, then the driver may depress the accelerator pedal (1) excessively, thereby causing the vehicle to accelerate faster than necessary.